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From: Xunlei Pang <xlpang@126.com>
To: linux-kernel@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Juri Lelli <juri.lelli@gmail.com>,
	Xunlei Pang <pang.xunlei@linaro.org>
Subject: [PATCH v2 2/4] sched/deadline: Remove cpu_active_mask from cpudl_find()
Date: Thu, 29 Jan 2015 23:53:18 +0800	[thread overview]
Message-ID: <1422546800-2935-2-git-send-email-xlpang@126.com> (raw)
In-Reply-To: <1422546800-2935-1-git-send-email-xlpang@126.com>

From: Xunlei Pang <pang.xunlei@linaro.org>

cpu_active_mask is rarely changeable, so remove this operation
to gain a little performance.

If there is a change in cpu_active_mask, rq_online_dl() and
rq_offline_dl() should take care of it normally, so cpudl::
free_cpus carries enough information for us.

For the rare case(causing a task put onto a dying cpu) which
rq_offline_dl() can't handle timely, then it can be handled
through _cpu_down()->...->multi_cpu_stop()->migration_call()
->migrate_tasks(), preventing the task from hanging on the
dead cpu.

Signed-off-by: Xunlei Pang <pang.xunlei@linaro.org>
---
 kernel/sched/cpudeadline.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index fd9d3fb..c6acb07 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -108,8 +108,7 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
 	const struct sched_dl_entity *dl_se = &p->dl;
 
 	if (later_mask &&
-	    cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed) &&
-	    cpumask_and(later_mask, later_mask, cpu_active_mask)) {
+	    cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed)) {
 		best_cpu = cpumask_any(later_mask);
 		goto out;
 	} else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&
-- 
1.9.1



  reply	other threads:[~2015-01-29 16:02 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-29 15:53 [PATCH v2 1/4] sched/deadline: Modify cpudl::free_cpus to reflect root_domain::online Xunlei Pang
2015-01-29 15:53 ` Xunlei Pang [this message]
2015-01-29 15:53 ` [PATCH v2 3/4] sched/deadline: Fix wrong cpudl_find() in check_preempt_equal_dl() Xunlei Pang
2015-01-29 15:53 ` [PATCH v2 4/4] sched/rt: Consider deadline tasks in cpupri_find() Xunlei Pang

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